1. Field of the Invention
The present invention relates to a varifocal optical device. More particularly, the present invention relates to a varifocal optical device of using an actuator with areas, which are bending-deformed in different directions to each other.
2. Description of the Related Art
A modern wireless mobile device is developing as a multipurpose electronic apparatus including various functions, such as a camera function, a game function, a music reproducing function, a broadcasting function, an internet function, etc., besides a telephone function and a message transmission function. With this, it is making an attempt to incorporate more functions in less space.
However, since a camera module is made up of a lens, an image sensor, a printed circuit board, etc. causing the increase of volume and thickness, it is difficult for the camera module to reduce a size. Particularly, although to improve an image in quality, the camera module needs an auto focusing function, an optical image stabilizing function, a zoom function, etc., it is difficult to add such functions into the camera module due to an restriction in size.
As typical methods for embodying the auto focusing function in the conventional camera, there are known a method of using a stepping motor, a method of using a voice coil motor, a method of using a piezoelectric actuator, a method of using a liquid lens, etc. Among these methods, the method of using the stepping motor and the method of using the voice coil motor are disadvantageous in that it is difficult to miniaturize a size of the camera module. The method of using the piezoelectric actuator presents a problem in that a maximum strain is small and a processing temperature is high. Also, the method of using the liquid lens presents a problem in that it is difficult to fill in a liquid without generating bubbles.